Insulation type step-up converter

1. An insulation type step-up converter, comprising: a core including a middle leg, a first outer leg spaced from the middle leg and arranged to extend in a direction identical to the middle leg, and a second outer leg spaced from the middle leg opposite to the first outer leg; a first primary-side coil arranged between the first outer leg and the middle leg; a second primary-side coil arranged between the second outer leg and the middle leg; a secondary-side coil wound around the middle leg, overlapping at least part of each of the first and second primary-side coils, and spaced from the at least part of each of the first and second primary-side coils; a third primary-side coil arranged between the first outer leg and the middle leg, overlapping at least part of the secondary-side coil, and spaced from each of the first primary-side coil and the secondary-side coil; a fourth primary-side coil arranged between the second outer leg and the middle leg, overlapping at least part of the secondary-side coil, and spaced from each of the second primary-side coil and the secondary-side coil; and a switching element configured such that it can be controlled to be on/off so as to cause electric currents in opposite directions to each other to flow simultaneously in the first and second primary-side coils, and configured such that it can be controlled to be on/off so as to cause electric currents in opposite directions to each other to flow simultaneously in the third and fourth primary-side coils, and configured such that it can be controlled to be on/off so as to cause electric currents to flow alternately in the first and second primary-side coils, and the third and fourth primary-side coils.

2. The insulation type step-up converter according to claim 1 , wherein the first and second primary-side coils are arranged on layers different from each other, and the third and fourth primary-side coils are arranged on layers different from each other.

3. The insulation type step-up converter according to claim 1 , wherein the first, second, third, and fourth primary-side coils are formed of a metal plate, the first and fourth primary-side coils are arranged on an identical layer, and the second and third primary-side coils are arranged on an identical layer, and the first and fourth primary-side coils are connected to each other by a connecting portion formed of the metal plate, and the second and third primary-side coils are connected to each other by a connecting portion formed of the metal plate.

4. The insulation type step-up converter according to claim 1 , wherein the first and second primary-side coils are arranged on a layer identical to each other, and the third and fourth primary-side coils are arranged on a layer identical to each other.

5. The insulation type step-up converter according to claim 2 , wherein the first, second, third, and fourth primary-side coils are formed of a metal plate, the first and fourth primary-side coils are arranged on an identical layer, and the second and third primary-side coils are arranged on an identical layer, and the first and fourth primary-side coils are connected to each other by a connecting portion formed of the metal plate, and the second and third primary-side coils are connected to each other by a connecting portion formed of the metal plate.

6. The insulation type step-up converter according to claim 1 , wherein each of the first, second, third, and fourth primary-side coils extends linearly in plan view.

7. The insulation type step-up converter according to claim 1 , wherein one end of a pair of ends of each of the first, second, third, and fourth primary-side coils leads to one of a radiator or a housing as a reference potential.

8. The insulation type step-up converter according to claim 1 , further comprising: a rectifier element configured to rectify a positive and negative voltage output from the secondary-side coil; and a smoothing circuit configured to smooth the voltage rectified by the rectifier element.